U.S. patent number 5,139,576 [Application Number 07/665,972] was granted by the patent office on 1992-08-18 for method and a horizontal pipeline pig launching mechanism for sequentially launching pipeline pigs.
This patent grant is currently assigned to Western Gas Processors, Ltd.. Invention is credited to Gary W. Davis.
United States Patent |
5,139,576 |
Davis |
August 18, 1992 |
Method and a horizontal pipeline pig launching mechanism for
sequentially launching pipeline pigs
Abstract
A method and apparatus for sequential launching a plurality of
pipeline pigs in serial manner into a gas transmission pipeline.
The pig launching system incorporates a tubular magazine for
receiving a plurality of pigs and having a free piston movably
disposed therein. A source of hydraulic fluid medium is provided
and is injected into the magazine behind the free piston for
movement of the free piston and the pigs for pig launching. A gas
energized liquid pump is operated by gas pressure from the gas
transmission pipeline under the control of a timer operated gas
supply valve for selective introduction of hydraulic fluid medium
into the magazine. A control panel incorporating control circuitry
is programmable to achieve timed launching of the pigs into the
pipeline and shuts down the pig launching mechanism after each pig
has been launched. The control circuitry is also capable of
rendering an alarm signal if pig launching is not achieved within a
predetermined time period.
Inventors: |
Davis; Gary W. (Broomfield,
CO) |
Assignee: |
Western Gas Processors, Ltd.
(Denver, CO)
|
Family
ID: |
24672296 |
Appl.
No.: |
07/665,972 |
Filed: |
March 7, 1991 |
Current U.S.
Class: |
134/8; 134/18;
15/104.062; 15/3.5 |
Current CPC
Class: |
F16L
55/46 (20130101); B08B 9/0551 (20130101) |
Current International
Class: |
F16L
55/46 (20060101); F16L 55/26 (20060101); B08B
009/04 () |
Field of
Search: |
;134/8,18,22.11,22.12
;15/104.062,3.5,3.51 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Morris; Theodore
Assistant Examiner: Chaudhry; Saeed
Attorney, Agent or Firm: Jackson; James L.
Claims
What is claimed is:
1. A method for timed automatic sequential launching of serially
oriented pipeline pigs from a pig launching system having a tubular
pig storage and launching magazine into a gas transmission
pipeline, comprising:
(a) providing a source of hydraulic fluid medium;
(b) locating a free piston within said tubular pig storage and
launching magazine for motive contact with the last of said
serially oriented pipeline pigs, said free piston partitioning said
tubular pig storage and launching magazine into a hydraulic chamber
and a pig storage chamber having a launching opening for
communication with said pipeline;
(c) employing gas pressure from said gas transmission pipeline for
pressurizing said hydraulic fluid medium from said source;
(d) introducing the pressurized hydraulic fluid medium into said
hydraulic chamber for hydraulically induced movement of said free
piston and said serially oriented pipeline pigs toward said
launching opening while restraining launching movement of the first
of said serially oriented pipeline pigs;
(e) controllably releasing said restraining of said first of said
serially oriented pipeline pigs from said tubular pig storage and
launching magazine for launching movement thereof through said pig
launching opening and into said gas transmission pipeline by said
free piston acting under motive force developed thereon by said
pressurized hydraulic fluid; and
(f) successively controllably releasing and launching each of said
serially oriented pipeline pigs as set forth in paragraph (e)
above.
2. The method of claim 1, wherein said pig launching system
incorporates a gas energized liquid pump having its suction in
communication with said source of hydraulic fluid medium and its
discharge in communication with said hydraulic chamber of said
tubular pig storage and launching magazine, said method
including;
selectively communicating pressurized gas from said gas
transmission pipeline to said gas energized liquid pump for
energization thereof, said gas energized liquid pump delivering
said hydraulic fluid medium from said source to said hydraulic
chamber at a pressure exceeding the pressure of said gas
transmission pipeline, thus developing a differential pressure
across said free piston for inducing movement of said free piston
and said pig toward said launching opening.
3. The method of claim 2 wherein said pig launching system includes
a gas control valve for controlling communication of pressurized
gas from said gas transmission pipeline to said gas energized
liquid pump and further includes a timer control for opening and
closing said gas control valve according to a preprogrammed timed
sequence, said method including:
selectively opening said gas control valve responsive to signals of
said timer control for selective gas energization of said gas
energized liquid pump by gas pressure from said gas transmission
pipeline thus achieving selective operation of said gas energized
liquid pump for selective delivery of pressurized hydraulic fluid
medium from said source into said hydraulic chamber.
4. The method of claim 3, including:
(a) detection of pig launching from said launching opening into
said gas transmission pipeline and providing an electrical signal
to said timer control; and
(b) closing said gas control valve by said timer control responsive
to said pig launching signal to thus deenergize said gas energized
liquid pump.
5. The method of claim 4, including:
(a) automatically closing said gas control valve after passage of a
predetermined period of time in absence of pig launching signal to
said timer control; and
(b) rendering an alarm signal indicative of automatic timer
controlled gas valve closure to identify failure of pig
launching.
6. The method of claim 1, wherein said pig launching system
incorporates:
(a) a launching barrel to receive pipeline pigs released from said
magazine, said pig launching barrel being connected to and forming
part of said gas transmission pipeline; and
(b) a launching valve being positioned between said magazine and
said pig launching barrel, and when open, permitting passage of
pigs therethrough during launching, said launching valve, when
closed, isolating said magazine from the gas pressure of said gas
transmission pipeline.
7. The method of claim 1, including:
(a) isolating said magazine from the pressure of said gas
transmission pipeline;
(b) loading a quantity of pipeline pigs into said magazine in
serial fashion;
(c) placing a free piston into said magazine behind the last of
said pipeline pigs;
(d) placing a piston stop within said magazine behind said free
piston;
(e) closing and sealing said magazine;
(f) introducing gas pressure from said gas transmission pipeline
into said magazine ahead of said free piston to establish a
pressure balanced condition across said launching valve;
(g) opening said launching valve;
(h) for serial launching of said pipeline pigs from said magazine
into said gas transmission pipeline selectively using gas pressure
from said gas transmission pipeline to impart said pressure to said
hydraulic fluid medium within said hydraulic chamber for a
sufficient period of time for launching a single piston from said
magazine into said gas transmission pipeline; and
(i) discontinuing pressurization of said hydraulic fluid medium by
said gas pressure from said gas transmission pipeline subsequent to
launching each of said pigs from said magazine.
8. The method of claim 7, wherein a gas energized liquid pump is
disposed with its liquid suction in communication with said source
of hydraulic fluid medium and with its discharge in communication
with said hydraulic chamber and a gas supply conduit coupled with
said gas transmission pipeline is also coupled in gas supplying
driving relation with said gas energized liquid pump and a timer
controlled valve is located in said gas supply conduit for
selective control of gas supply to said gas energized liquid pump,
said method including:
(a) for initiation of pig launching, opening said gas supply valve
to initiate pumping of hydraulic fluid medium from said source into
said hydraulic chamber at a pressure exceeding gas pressure within
said magazine thus moving said free piston and said pigs in the
direction of launching; and
(b) upon detection of pig launching from said magazine into said
gas transmission pipeline, closing said gas supply valve to cease
liquid pump operation and to discontinue introduction of hydraulic
fluid medium into said hydraulic chamber.
9. A pipeline pig launching mechanism for sequentially launching
pipeline pigs into a gas transmission pipeline, comprising:
(a) a magazine for containing a plurality of pipeline pigs arranged
in serial orientation, said magazine having a launching end in
communication with said gas transmission pipeline and a loading end
forming an access opening;
(b) a closure for selectively opening and closing said access
opening permitting loading of pipeline pigs into said magazine;
(c) a free piston being movably disposed within said magazine and
having pig moving contact with the last of said plurality of
serially oriented pipeline pigs and capable of moving said pipeline
pigs toward said launching end of said magazine;
(d) means for releasably restraining launching movement of the
first of said pipeline pigs and for preventing launching of said
free piston;
(e) means for controllably and sequentially releasing said first of
said pipeline pigs for launching movement thereof by said free
piston;
(f) a source of hydraulic fluid medium; and
(g) means responsive to gas pressure from said gas transmission
pipeline for pressurizing said hydraulic fluid medium from said
source and injecting said pressurized hydraulic fluid medium into
said magazine behind said free piston at a pressure exceeding the
pressure of said gas transmission pipeline to thus apply motive
force to said free piston for movement of said plurality of
pipeline pigs to said launching end of said magazine for sequential
launching of the same into said gas transmission pipeline.
10. The pipeline pig launching mechanism of claim 9, wherein said
means for pressurizing said hydraulic fluid medium comprises:
(a) a gas energized liquid pump having its liquid suction in
communication with said source of hydraulic fluid medium and having
its discharge in communication with said magazine;
(b) a gas supply conduit having one end thereof in communication
with said gas transmission pipeline and the opposite end thereof
coupled in gas supplying relation with said gas energized liquid
pump;
(c) a gas supply valve being coupled in said gas supply conduit and
when open, permitting the flow of gas through said conduit to said
gas energized liquid pump; and
(d) control means for selectively opening said gas supply valve for
launching of one of said pipeline pigs from said magazine into said
gas transmission pipeline and closing said gas supply valve upon
launching of each of said pipeline pigs.
11. The pipeline pig launching mechanism of claim 10, wherein said
control means comprises:
a control panel having an electrical timing circuit coupled in
electrically controlling relation with said control valve and being
capable of selectively opening and closing said control valve for
selective deviation of said gas energized liquid pump.
12. The pipeline pig launching mechanism of claim 11,
including:
a pump safety valve being coupled within said gas supply conduit
downstream of said gas control valve opening of said pump safety
valve initiating a timing sequence of said timer circuit of said
control panel for initiation of a timed sequence of opening and
closing of said gas supply valve.
13. The pipeline pig launching mechanism of claim 12,
including:
(a) means for detecting launching of a pipeline pig from said
magazine into said gas transmission pipeline and for providing an
electrical signal to said control panel circuitry indicating that
pig launching has taken place; and
(b) said control circuitry of said control panel closing said gas
supply valve upon receiving said pig launching signal.
14. The pipeline pig launching mechanism of claim 9, including:
(a) a launching barrel being coupled in flow conducting relation
with said gas transmission pipeline;
(b) a launching valve being disposed between said launching barrel
and said magazine, when open, said launching valve permitting
passage of pigs therethrough for launching, when closed, said
launching valve isolating said magazine from the gas pressure of
said gas transmission pipeline; and
(c) a differential pressure sensor being coupled between said
launching barrel and said gas transmission pipeline and having an
electrical conductor coupled with the control circuitry of said
control panel, upon detection of a predetermined differential
pressure indicating pig launching to said gas transmission
pipeline, said differential pressure sensor transmitting a signal
through said conductor to said control circuitry.
15. The pipeline pig launching mechanism of claim 9, including:
(a) a pig stop member being removably positioned within said
magazine behind said piston pig to thus limit pressure induced free
piston movement toward said closure to thus define a hydraulic
chamber between said free piston and said closure; and
(b) said discharge of said gas energized liquid pump being in
communication with said hydraulic chamber.
16. The pipeline pig launching mechanism of claim 15,
including:
(a) a drain conduit being in communication with said hydraulic
chamber of said magazine and also being in communication with said
source of hydraulic fluid medium; and
(b) a drain control valve being coupled into said drain conduit and
being selectively opened to permit gas energized return of
hydraulic fluid medium from said hydraulic chamber to said source
of hydraulic fluid medium as said free piston is moved toward said
closure by gas pressure within said magazine.
17. The pipeline pig launching mechanism of claim 9, wherein said
gas energized liquid pump comprises:
(a) a double acting piston pump mechanism having opposed gas and
liquid cylinders, said liquid cylinder being of smaller dimension
as compared to said gas cylinder;
(b) gas and liquid pistons being movable disposed within said
respective gas and liquid cylinders, said pistons being coupled by
a piston shaft;
(c) said liquid cylinder having a suction in communication with
said source of hydraulic fluid medium and having a discharge in
communication with said hydraulic chamber of said magazine; and
(d) responsive to the flow of pressurized gas from said gas
transmission pipeline, said gas piston reciprocating and driving
said liquid piston in sequential reciprocating manner to pump said
hydraulic fluid medium from said source to said hydraulic chamber.
Description
FIELD OF THE INVENTION
This invention relates generally to apparatus for introducing pigs
into pipelines for the purpose of cleaning such pipelines of debris
such as sediment and for clearing the pipeline of fluid such as
water, distillate, etc. which may become trapped in low lying areas
of the pipeline. More specifically, the present invention relates
to an automatic horizontally disposed cup pig launcher which
functions sequentially according to the control of a timer
mechanism for automatic launching of cup pigs from a pig storage
magazine into a gas pipeline and which utilizes a liquid
composition which is driven by a gas energized positive
displacement pump having gas pressure from the pipeline as its
driving fluid medium.
BACKGROUND OF THE INVENTION
In the operation of gas pipelines water and hydrocarbon vapors tend
to condense especially during pressure changes across the valves,
orifice fittings, pumps, etc. thereby causing the build-up of
liquid deposits in the pipeline. These liquid deposits tend to
become entrapped in low places in the pipeline and otherwise reduce
the cross-section of dimension of the pipeline passages so that
unless regularly cleaned of such deposits, the production capacity
of the pipeline will be reduced.
Large transportation lines for natural gas are frequently cleaned
of condensate, sediment and other debris that might be present in
the gas, such cleaning being accomplished by various types of
cleaning devices, typically referred to as "pigs" which are passed
through the pipeline along with the flowing gas. Various types of
pigs such as spheres, line scrapers, bullets, cup pigs, etc. are
forced through the pipelines at frequent intervals for the purpose
of forcing liquid matter through the pipeline along with the
flowing gaseous medium. In some cases, high pressure pipelines
transporting fluid material are required to carry a liquid phase
simultaneously with the gaseous phase. Such liquids may be present
in the gas when it is injected into the pipeline as in full well
stream transport or liquids such as drip gasoline or crude oil may
be injected into a flowing gas stream to be transported along with
the gas.
Where liquid constituents are present in a gas pipeline especially
where several different liquids may be transported along with the
flowing gas, it will be appropriate to utilize pigs, such as cup
pigs, for the purpose of separating the liquids. Accordingly, it is
desirable to provide a pig launching mechanism having the
capability of sequentially launching a plurality of pigs such as
cup pigs into a continuously flowing gas pipeline so that the
pipeline will remain clear of any accumulations of sediment,
condensate, and so that liquid constituents being transported by
the pipelines can remain separated.
SUMMARY OF THE INVENTION
It is a principle feature of the present invention to provide a
novel system for sequential launching of cup pigs into a
continuously flowing pipeline.
It is also a feature of this invention to provide novel plurality
of pigs into a continuously flowing pipeline according a timed
sequence.
It is an even further feature of this invention to provide a novel
pig launching system which is of automatically actuatable nature
and employs gas pressure from the pipeline to provide the motive
force for pig launching operations.
It is an even further feature of this invention to provide a novel
horizontal cup pig launcher which utilizes a liquid constituent
which is compatible with the gas and liquid being handled by the
pipeline and which achieves sequential launching of the pigs into
the pipeline
It is another feature of this invention to provide a novel pig
launching mechanism which employs gas pressure from the pipeline
for driving a pump, which pump in turn drives a liquid constituent
that functions hydraulically to achieve sequential launching of the
pigs from a pig storage magazine
Briefly, a horizontal automatic cup pig launcher constructed in
accordance with the present invention incorporates a pig storage
magazine which is typically horizontally disposed and which is in
communication with a gas transmission pipeline by means of a
launching valve. A plurality of cup pigs are positioned within the
magazine and a piston which is driven by a liquid constituent such
as methanol (CH.sub.3 OH) is driven by a pump to impart motive
force to the launching piston. The pump for energizing the piston
driving liquid constituent is energized by gas pressure from the
pipeline and achieves a piston driving liquid pressure that is
greater than the gas pressure of the pipeline. A control system is
employed to achieve sequential launching of the pigs into the gas
transmission pipeline according to a timing sequence which may be
varied to suit the needs of those in charge of the pipeline. For
example, the timer is programmable to launch from two to six pigs
in a twenty-four hour period without necessitating the presence of
personnel at the pig launching facility and without requiring (but
allowing) remotely controlled actuation of the pig launcher.
Within the scope of the present invention is a method or process
for utilization of pipeline gas pressure for developing hydraulic
pig launching pressure The method also employs a timer,
incorporated within a control panel, which establishes the timing
sequence for achieving sequential pig launching. Also, the present
invention incorporates the method or process for insuring the
safety of the pig storage magazine and for opening and reloading
the magazine with additional pigs for subsequent launching thereof
and for rendering the launching magazine operational.
BRIEF DESCRIPTION OF THE DRAWINGS
So that the manner in which the above recited features, advantages
and objects of the present invention are attained and can be
understood in detail, a more particular description of the
invention, briefly summarized above, may be had by reference to the
embodiments thereof which are illustrated in the appended
drawings.
It is to be noted, however, that the appended drawings illustrate
only typical embodiments of this invention and are therefore not to
be considered limiting of its scope, for the invention may admit to
other equally effective embodiments
In the Drawings
The single FIGURE of the drawings is a partially schematic
illustration of an automatic cup pig launching mechanism
representing the preferred embodiment of the invention and
including pneumatic and hydraulic circuitry for operation of the
pig launching mechanism.
DETAILED DESCRIPTION OF PREFERRED
Referring now to the drawing, a horizontal automatic cup pig
launcher according to the present invention is illustrated
generally at 10 and includes a pig storage magazine 12 which is
typically horizontally oriented but which may assume any other
suitable position without departing from the spirit and scope of
this invention. The tubular magazine 12 is coupled by means of a
90.degree. elbow 14 with a launching valve V.sub.a which may be a
gate valve, ball valve or a valve of any other suitable character
having a straight through flow passage of sufficient dimension to
allow cup pigs 16 to pass therethrough to a launching barrel 18.
The launching barrel has its inlet 22 coupled with the incoming
pipeline section 24 and its outlet coupled by a reducer 26 to the
downstream pipeline section 28.
For the purpose of detecting actual launching of a pig into the
downstream pipeline section 28, a conduit 30 has one end thereof
coupled with the launching barrel 18 and the opposite end coupled
with the downstream flow conduit 28. A differential pressure sensor
DP is coupled into the conduit 30 for sensing pressure of both the
launching valve and the downstream pipeline. The differential
pressure sensor may be selectively isolated from pipeline pressure
by isolation valves 32 and 34. The differential pressure sensor DP
is coupled by an electrical signal output conductor 36 to the
electrical control circuitry of a control panel. To protect the
control panel from inclement weather conditions, the control panel
and other components of the pig launching mechanism are enclosed
within a small building such as shown in broken lines at B. The
building B is provided with a catalytic heater which is capable of
being automatically energized under the control of the circuitry of
the control panel, which is transmitted via electric conductor 38,
and in response to internal building temperature being sensed by a
temperature sensor T.
The cup pigs 16 within the magazine 12 will be sequentially
launched through the elbow 14 and launching valve VA into the
launching barrel 18 in accordance with a launching sequence that is
determined by the programmable solid state electronic circuitry of
the control panel. Sequential and serial launching of the pigs 16
is also accomplished through the use of gas pressure from the
pipeline as will be explained in detail hereinbelow. The launching
magazine is provided with a pig restraint and release mechanism 40
which provides additional resistance to the forward movement of the
pigs 16 preventing multiple launches and prevents launching of the
piston 44 In order to accomplish movement of the pigs 16 toward the
respective launching positions thereof, a free piston 44 is
positioned within the magazine 12 and is provided with appropriate
seals for sealing relation thereof with the cylindrical internal
surface 46 of the magazine. The free piston 44 engages the last of
the serially oriented pigs 16 and is responsive to hydraulic
pressure for applying sufficient force to the pigs to move them
toward the respective launching positions thereof.
The magazine 12 defines a pig loading opening 48 which is
surrounded by a closure support flange 50. A closure mechanism 52
is receivable in sealed relation by the flange 50 and is movable
from the closed and sealed position shown in the figure to an open
position to permit loading of the pigs into the magazine 12.
Preferably, the closure 52 is supported from the magazine by a
hinge and is capable of being manually pivoted to its open position
after being unlocked from its closed and sealed position.
The free piston cooperates with the loading end of the magazine 12
to define a hydraulic chamber 54 which is adapted by appropriate
piping to receive a hydraulic fluid medium from a hydraulic storage
facility 56 It is desirable to limit movement of the free piston 44
to the left or toward the loading opening of the magazine.
Accordingly, a piston stop element 58 is positioned within the
hydraulic chamber 54 and functions as a physical stop which is
engaged by the free piston 44 at the limit of piston movement.
Thus, both the free piston and the piston stop cooperate to form
the hydraulic chamber 54 within the elongate tube of the magazine.
If desired, the piston stop 58 may be a freely movable element
which is positioned within the hydraulic chamber 54, or in the
alternative, the piston stop may be a structural component of the
closure 52. In either case, however, its purpose is to limit
movement of the free piston 44 toward the loading opening 48 of the
magazine Even though the magazine defines an internal cylindrical
surface, the piston stop will permit the hydraulic chamber 54 to
retain at least a minimum volume of hydraulic fluid. At the
launching end of the magazine 12 the pig launch control apparatus
40-42 will stop movement of the piston 44 toward the launch
position after the last pig 16 has been launched The free piston
will always remain in the magazine except during the pig loading
procedure.
After the magazine 12 has been loaded with pigs 16, the piston pig
44 and the piston stop member 58, which activities are accomplished
with the launching valve V.sub.a in its closed position, it will be
appropriate to balance the pressure of the magazine with pipeline
pressure and to balance pressure across the free piston 44 within
the magazine. To accomplish these features, a conduit 59
communicates with the pipeline section 24 upstream of the launching
barrel 18 and is provided with an isolation valve 60. The conduit
59 is provided to communicate gas pressure from the pipeline into
the magazine 12 ahead or upstream of the free piston 44 under the
control of a valve V.sub.b. A conduit 62 coupled with conduit 59
conducts pipeline pressure to another conduit 64 which is in
communication with the hydraulic chamber 54. A valve V.sub.e in
conduit 62 controls admission of pipeline pressure from the conduit
62 into the hydraulic chamber. When valves V.sub.b and V.sub.e are
open, pipeline pressure is communicated into the magazine 12 and to
both the upstream and downstream sides of the piston 44. Thus, the
free piston 44 is pressure balanced when these valves are both
open. The conduit 64 is provided with an over-pressure control
device 66 such as a pressure regulator. A conduit 68 from the
pressure regulator 66 is coupled with a conduit 70 leading to the
storage vessel 56 for a quantity of hydraulic fluid such as
methanol (methyl alcohol). The liquid storage vessel therefore
achieves its pressurization from the gas energy of the pipeline.
The pressure regulator maintains the storage vessel at a desired
pressure to assist in the flow of liquid from the storage vessel to
the hydraulic chamber 54 as will be discussed hereinbelow. Storage
vessel pressure, however, is insufficient to achieve movement of
the free piston within the magazine.
As mentioned above, pressure from the pipeline is utilized to
provide the motive force for pressurized transfer of the hydraulic
fluid medium from the storage vessel 56 to the hydraulic chamber 54
of the magazine. To accomplish this feature a conduit 72 is coupled
with the pipeline section 24 upstream of the launching barrel 18
and includes isolation valves 74 and 76 for selectively controlling
communication of pipeline pressure for liquid pumping activity. The
conduit 72 also includes an over-pressure control mechanism 78 such
as a pressure regulator. Downstream of the pressure regulator is
provided a timer controlled gas supply valve V.sub.f which may, for
example, be controlled by a solenoid 80 that is energized by the
circuitry of the control panel via an electrical conductor 82. A
pump safety valve V.sub.g is also provided in the conduit 72
downstream of the pressure regulator 78 and the gas supply valve
V.sub.f to insure initial opening of valve V.sub.f and to initiate
start of the timing sequence for pig launching.
The pump 84 incorporates a large cylinder 86 having a piston 88
movably disposed therein. A cylinder 90 of smaller dimension as
compared to the cylinder 86 is provided with an internally movable
piston 92 which is of smaller dimension as compared to the piston
88. Regulated pressure from the conduit 72 enters the piston
chamber 94 and acts upon the exposed surface area of the piston 88,
thus developing a piston force that is transmitted via an actuator
stem 96 to the smaller piston 92 thus driving the liquid
pressurizing piston 92 for its power stroke within the cylinder 90.
Upon movement of the interconnected pistons 88 and 92 in the
opposite direction by pressure introduced into the cylinder 86
above the piston 88, gas within the piston chamber 94 is vented
through vent line 98 under control of a check valve or some other
suitable control mechanism, not shown and the piston 92 will draw
additional liquid into the pumping chamber into the cylinder 90 via
suction line 101.
The hydraulic fluid medium is transferred via its gas pressure and
its liquid head pressure through a suction conduit 101 to the pump
chamber 102 through an isolation valve 104. Upon pressurization by
the piston 92, liquid within the pump chamber 102 is forced through
a pump discharge conduit 106 to the hydraulic chamber 54 through
open isolation valves 108 and 110. To insure that pump discharge
pressure does not exceed a predetermined value, a return conduit
112 is coupled with the supply conduit 100 and discharge conduit
106 of the pump cylinder 90 and an over-pressure control mechanism
such as a pressure regulator 114 is provided to vent any excessive
pressure from the pump discharge conduit 106 back to the storage
vessel 56.
In order to facilitate the loading of pigs 16 into the magazine 12
after all of the pigs have been launched, it will be appropriate to
return the hydraulic fluid medium from the hydraulic chamber 54 to
the storage vessel 56. For this purpose, a return conduit 116 is
provided having a control valve V.sub.c located therein.
Additionally, a return conduit 118 is provided which is coupled
with conduit 106 between the isolation valve 110 and the hydraulic
chamber 54. The conduit 118 is controlled by a valve V.sub.i and is
in communication with conduit 100. Consequently, when valve V.sub.i
is opened, the hydraulic fluid medium within the chamber 54 may be
returned through conduits 118 and 100 to the storage facility 56.
Likewise, when the valve V.sub.c is opened the hydraulic fluid
medium will be returned from the chamber 54 through the conduits
116 and 70 to the storage chamber 56.
As mentioned above, the building or enclosure B is provided with a
catalytic heater for the purpose of maintaining the building at a
sufficiently high temperature even during extremely cold conditions
that the electronic circuitry of the control panel will remain at
its proper operational efficiency at all times. The catalytic
heater is designed to utilize natural gas from the pipeline for its
operation. A supply conduit 120 is provided having an isolation
valve 122 and a pressure regulator 124 for supplying natural gas to
the catalytic heater at a pressure range that is optimum for heater
operation. Under the control of the circuit 38 the control panel
will automatically operate the catalytic heater in response to
signals from the temperature sensor T.
OPERATION
Pig Loading Procedure
The procedure for achieving loading of a plurality of pigs into the
magazine 12 basically comprises 16 steps or activities which
require various valve positions and various positions of the
closure 52. These steps or activities can be visualized quite
readily by inspection of the various valve and closure positions as
set forth in the following chart:
__________________________________________________________________________
STEP VALUE 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
__________________________________________________________________________
V.sub.a O O C C C C C C C C C C C C C O O V.sub.b C C C C C C C C C
C C C C O C C C V.sub.c C C C O O C C C C C C C C C C C C V.sub.d C
C C C C O O O O O O O C C C C C V.sub.e C C C C O C C C C C C C C C
C C C V.sub.f A A A A A A A A A A A A A A A A A V.sub.g O C C C C C
C C C C C C C C C C O V.sub.h C C C C C C O O O O O O C C C C C
V.sub.i C C C C C C C C C C C O C C C C C Closure C C C C C C O O O
O O C C C C C C
__________________________________________________________________________
Across the top of the chart are identified 16 different activities.
Downwardly along the left side of the chart each of the valves is
identified, its position being indicated by the letters "C"
(closed), "O" (open) and "A" (automatically controlled). The
positions of the closure element 52, i.e., opened or closed are
indicated at each of the steps according to the chart.
Step 1--To initiate the pig loading procedure the pump safety valve
V.sub.g is closed to insure that the gas energized hydraulic pump
84 can not start its operation. In this regard, it should be born
in mind that operation of the pump 84 will begin automatically upon
the supply of pressurized gas therethrough upon opening of the
valve V.sub.f. Valve V.sub.f opens responsive to opening of the
pump safety valve V.sub.g and is closed in response to timed
actuation according to the programming of the control panel
circuitry. The valve V.sub.f is also capable of closure by the
control panel circuitry if failure of pig launching occurs.
Step 2--It should be born in mind that at the beginning of a pig
loading procedure the magazine 12 will be under line pressure from
the pipeline because the launching valve V.sub.a will be open. To
isolate the magazine 12 from pipeline pressure the launching valve
V.sub.a will be closed. After the launching valve has closed the
magazine 12 will remain under line pressure until its pressure is
bled to the atmosphere or otherwise to a designated receptacle. The
magazine pressure on each side of the free piston 44 may be
visually observed through inspection of pressure indicators
PI.sub.1 and PI.sub.2.
Step 3--It will be appropriate to shift the free piston 44 towards
the closure 52 to thus permit the piston stop 58 and the free
piston to be removed from the magazine. This is accomplished by
slowly opening the valve V.sub.c which allows gas pressure within
the magazine to move the free piston 44 to the left toward the
piston stop 58 while the hydraulic fluid medium is being bled
through valve V.sub.c and conduits 116 and 70 to the storage vessel
56. This activity will be continued until the free piston has come
into contact with the piston stop 58. At this point, it will be
observed that a quantity of the hydraulic fluid medium will remain
within the chamber 54 and the magazine 12 will remain under gas
pressure though the pressure will have been reduced somewhat by
virtue of piston movement by the expanding gas.
Step 4--In order to transfer the remaining hydraulic fluid medium
from the chamber 54 to the storage vessel 56 valve V.sub.e will be
slowly opened, thereby allowing gas pressure from the pipeline
flowing through valve 60 conduits 59 and 62 and valve V.sub.e to
develop a positive gas pressure within the chamber 54. In order to
prevent the free piston 44 from being moved to the right as the
injected gas pressure is displacing the hydraulic fluid medium from
the chamber 54 through conduit 116 and 70 through the open valve
V.sub.c, it is important to insure that the pressure detected by
pressure indicator PI.sub.1 does not exceed the pressure detected
by pressure indicator PI.sub.2. This insures that piston movement
in the opposite direction does occur as the hydraulic chamber is
being cleared of liquid. As soon as the introduction of gas
pressure from the chamber 54 through conduits 116 and 70 is
detected, all of the hydraulic fluid medium will have been
displaced from the chamber 54. At this point, valve V.sub.e is
closed to prevent any further introduction of gas pressure into the
chamber 54.
Step 5--At this point, it must be insured that valves V.sub.a,
V.sub.b, V.sub.c and V.sub.e are closed to insure that the magazine
12 is isolated from fluid pressure from any source. The vent valve
V.sub.d is then slowly opened to vent the pressure from chamber 54
to the atmosphere. At this point there will be pressure present in
the magazine 12 between the free piston 44 and the closed launching
valve V.sub.a. This pressure will maintain free piston in contact
with the piston stop 58. Next, the vent valve V.sub.h is opened,
thereby venting pressure from the magazine 12 to the atmosphere
After this has been accomplished, the pressure on each side of the
free piston 44 will be atmospheric pressure. The pressure
indicators PI.sub.1 and PI.sub.2 should be at 0 or atmospheric
pressure and both the vent valves V.sub.d and V.sub.h should be
open.
Step 6--After operation personnel has made absolutely certain that
no gas pressure is present within the magazine 12 on either side of
the free piston 44, the closure member 52 is unlocked and
opened.
Step 7--The piston stop 58 and the free piston 44 are then removed
from the magazine. It should be born in mind, that if piston stop
58 is in assembly with the closure, opening of the closure will
also accomplish removal of the piston stop.
Step 8--The appropriate number of pipeline pigs are then inserted
into the magazine. Typically, the magazine will be filled with six
or seven cup pigs but it should be born in mind that such is not
limiting as to the spirit and scope of this invention. The magazine
may be of any suitable length and thus the pigs 16 may be of any
suitable number.
Step 9--After the magazine has been appropriately loaded with
pipeline pigs, the piston pig and the pig stop are then inserted
into the magazine.
Step 10--The closure member 52 is then properly positioned with
respect to the flange 50 at the opening 48 of the magazine and is
properly locked and sealed.
Step 11--The hydraulic fluid supply valve V.sub.i is then opened
and allowed to remain open until hydraulic fluid is detected to be
present at the open vent valve V.sub.d thus indicating that the
chamber 54 will have been completely filled with the hydraulic
fluid medium. Filling of the chamber 54 could be accomplished
solely due to the head pressure of the hydraulic pressure within
the storage vessel 56. More practically, however, gas pressure is
introduced into the storage vessel 56 through conduits 59, 62, 64,
68 and 70 by opening of valve V.sub.e. The pressure regulator 66
will control the gas pressure condition within the storage vessel.
The various isolation valves throughout the conduit system will
remain open unless isolation of specific components of the system
is desired such as for servicing, repair or replacement. Only the
control valves V.sub.a -V.sub.i will be opened or closed to control
operation of the pig launching system.
Step 12--The magazine pressure supply valve V.sub.b is slowly
opened to introduce pressure from the pipeline 24 into the magazine
between the closed launching valve V.sub.a and the free piston 44.
After a time, the magazine will reach pipeline pressure.
Step 13--The magazine pressure supply valve V.sub.b is then closed
to render the magazine 12 to appropriate conditions for subsequent
operations and to isolate the magazine from pipeline pressure
except through the launching valve V.sub.a.
Step 14--The launching valve V.sub.a is then moved to its open
position, such movement being relatively easy because, though under
line pressure, no pressure differential will exist across the
launching valve.
Step 15--The pump safety valve V.sub.g is then opened to permit
initiation of sequential timer opening of the control valve V.sub.f
for operation of the gas driven pump 84.
Pig Launching Procedure
The circuitry of the control panel is programmed, as mentioned
above to launch from two to six pigs from the magazine into the
pipeline during each 24 hour period. The control timer of the
control panel initiates its start sequence by opening the control
valve V.sub.f thereby allowing gas pressure from the pipeline under
the control of pressure regulator 78 to pass through the open pump
safety valve V.sub.g into the piston chamber 94 of the large
cylinder 86. The pump pistons will then begin to reciprocate,
drawing hydraulic fluid from the supply conduit 100 into the piston
chamber 102 during each suction stroke and discharging pressurized
hydraulic fluid from the chamber 102 into the discharge conduit 106
during each power stroke of the piston 92. Thus the hydraulic fluid
(methanol) is forced into the chamber 54 of the magazine, thereby
developing a pressure differential across the free piston 44 which
develops sufficient force to urge the free piston and the pigs 16
in the direction of launching. The first of the serially arranged
pigs 16 is restrained by element 42 until sufficient pressure is
developed in the chamber 54 to advance a pig past the stop. When
this occurs, the first pig will be forced to the right and will
slide under the influence of gravity through the passage of the
elbow 14 and through the open launching valve V.sub.a into the
launching barrel 18. The flow of fluid from the pipelines through
the launching barrel will then force the piston into the pipeline
section 28 so that the pig will be forced through the pipeline by
the flowing fluid. Any condensate, sediment or other material which
is present within the pipeline will be forced by the pig through
the pipeline until the pig is caught by a pig trap at the terminus
of its movement.
The control panel circuitry is capable of detecting actual
launching of each pig. The differential pressure detector DP with
its isolation valves 32 and 34 open will detect internal pressure
fluctuations as the pig is launched into the pipeline section 28.
For example, when a 10 pound differential pressure signal occurs at
the differential pressure switch DP an electrical signal will be
conducted via the conductor 36 to the control panel circuitry. This
signal will cause the control panel circuitry to close the valve
V.sub.f, thereby stopping the supply of gas to the pump mechanism
84 and thereby ceasing pig movement by the free piston 44 within
the magazine 12. Simultaneously with closing of the valve V.sub.f a
signal is transmitted indicating that a pig has been launched
through the launching barrel, thus restarting the timing sequence
for subsequent pig launching.
The pig launching mechanism is also provided with a system to
discontinue the pig launching procedure in the event a malfunction
occurs. For example, the timer control valve V.sub.f is provided
with a timer limiting feature. In the event an appropriate
differential pressure signal is not detected by the differential
pressure sensor DP within a preselected period of time such as 10
minutes of the opening of the valve V.sub.f by the timer of the
control panel, the timer will automatically signal the valve
V.sub.f to close even though pig launching has not been detected
and to render and alarm signal so that the malfunction is
immediately reported. This timer protection control is variable to
suit the needs of the user. For example, automatic closure of the
valve V.sub.f by the timer may be varied between five minutes to 20
minutes to insure that the launching mechanism has adequate time to
achieve positive launching of each pig.
Automatic operation of the pig launching mechanism will then
continue until such time as the last pig has been launched and its
launching has been properly detected. After launching of the last
pig, the valve V.sub.f will be closed by the circuitry of the
control panel and the pig launching mechanism will then remain
inoperative until the magazine is subsequently reloaded with pigs
according to the loading procedure described above.
The hydraulic fluid medium that is contained within the storage
vessel 56 and is utilized for the pig launching procedure may take
any suitable liquid form that is compatible with the fluid being
controlled by the pipeline. For example, one suitable fluid that is
acceptable for use as hydraulic fluid in connection with the
transportation of natural gas and the liquids that are normally
associated therewith, may conveniently take the form of methanol,
CH3OH, also described as methyl alcohol. Other suitable liquids
that are capable of being utilized in conjunction with pipelines
handling petroleum products such as natural gas are diesel oil, jet
fuel, kerosene, etc.
In view of the foregoing, it is evident that the present invention
is one well adapted to attain all of the objects and features
hereinabove set forth, together with other objects and features
which are inherent in the apparatus disclosed herein.
As will be readily apparent to those skilled in the art, the
present invention may be produced in other specific forms without
departing from its spirit or essential characteristics. The present
embodiment, is therefore, to be considered as illustrative and not
restrictive, the scope of the invention being indicated by the
claims rather than the foregoing description, and all changes which
come within the meaning and range of the equivalence of the claims
are therefore intended to be embraced therein.
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